Question

Name important defence mechanisms in plants against herbivory.

Answer 1

1. For plants, herbivores act as their predators; nearly 25 per cent of all insects are known to be phytophagous, meaning they feed on plant sap and other parts of plants.
2. The problem is more severe for plants because, unlike animals, they cannot escape from their predators.
3. Plants have developed a wide range of morphological and chemical defences against herbivores to protect themselves.
4. Thorns and spines found in plants such as Acacia and Cactus are common morphological means of defence.
5. Some plants release toxins that poison attacking herbivores. Other plants produce complex chemical compounds that interfere with the attacker’s growth cycle or ability to digest the plant.
6. Plants have evolved secondary metabolites used in plant defence, known as antiherbivory chemicals. These defensive chemicals include nitrogen compounds (alkaloids, cyanogenic glycosides, benzoxazinoids), terpenoids, and phenolics.
7. The weed Calotropis, which grows in abandoned fields, produces highly poisonous cardiac glycosides. Because of these toxic substances, cattle and goats rarely graze on Calotropis.
8. These defense mechanisms have evolved to reduce damage from herbivores and ensure the survival of the plants.

Answer 2

Herbivores are plants natural predators. Plants have evolved many morphological and chemical defenses against herbivory. Acacia and cactus depend on thorns as their primary defense mechanism. Certain plants have compounds that can make herbivores sick, delay digestion, disrupt reproduction, or even kill them.